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Preconception maternal iodine status is associated with IQ but not with measures of executive function in childhood

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  • Sian M Robinson
  • Sarah R Crozier
  • Elizabeth Miles
  • Catharine Gale
  • Philip Calder
  • Cyrus Cooper
  • Hazel M Inskip
  • Keith M Godfrey

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Original languageEnglish
Pages (from-to)959-966
JournalJournal of Nutrition
Volume148
Issue number6
Early online date15 May 2018
DOIs
Publication statusPublished - Jun 2018

Abstract

Background: Adverse effects of severe maternal iodine deficiency in pregnancy on fetal brain development are well-established, but the effects of milder deficiency are uncertain. Most studies examine iodine status in pregnancy; less is known about iodine nutrition before conception.
Objective: We examined relationships between maternal preconception iodine status with offspring cognitive function, within a prospective mother-offspring cohort.
Design: Maternal iodine status was assessed using the ratio of iodine:creatinine concentrations (I/Cr) in spot urine samples (median period before conception 3.3 (interquartile range 2.2,4.7) years). Childhood cognitive function was assessed at age 6-7 years. Full scale IQ was assessed using the Wechsler Abbreviated Scale of Intelligence, and executive function using tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB). Analyses (n=654 mother-child dyads) were adjusted for potential confounders including maternal intelligence, education and breastfeeding duration. Results: Median (interquartile range) urinary iodine concentration was 108.4 µg/L (62.2-167.8) and I/Cr ratio 114 µg/g (76-164). Preconception I/Cr ratio was positively associated with child IQ, before and after (β=0.13 (95%CI 0.04, 0.21) /SD, P=0.003) adjustment for potential confounding influences. 8.9% of women had a preconception urinary I/Cr ratio <50 µg/g; compared to those with an I/Cr ratio ≥150 µg/g, their offspring IQ was 0.49 (95% CI 0.79, 0.18) SD lower. There were no associations with the executive function outcomes assessed using CANTAB, before or after adjustment for confounders. 
Conclusions: The association between iodine status before conception and child IQ provides some support for demonstrated links between low maternal iodine status in pregnancy and poorer cognitive function reported in other studies. However, given the negative effects on school performance previously observed in children born to iodine-deficient mothers, the lack of associations with measures of executive function in the present study was unexpected. Further data are needed to establish the public health importance of low preconception iodine status.

    Research areas

  • iodine, development, cognition, child, mental processes, mothers, executive function, cognitive ability

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